Many activities of an apparently random nature have been found to exhibit a deterministic phenomenon known as chaos, including but not limited to irregular pulsating behavior of living animal tissue. Recently, a strategy was developed tending to control a non-linear dynamic system in which a chaotic regime occurs. The critical features of the chaos phenomenon believed to make such control possible are short term predictability and extreme sensitivity of chaotic systems to perturbances of their initial conditions. A key to the control strategy lies in the fact that a chaotic system includes an infinite number of unstable periodic motions and never remains very long in any of such unstable motions, but continually switches from one periodic motion to another to thereby give an appearance of randomness. The chaos control strategy involves measurement of the current system parameter and identification of an unstable fixed point of interest representative of a system state plotted along with its stable and unstable directional manifolds. Such unstable fixed point and its accompanying manifolds shift in response to changes in system-wide parameters so that a feedback providing algorithm was developed for movement of the fixed point and manifolds toward the desired plotted system state point in response to control or modification of a selected system-wide parameter. As an alternative to moving the fixed point in accordance with a system-wide parameter, the system state point itself may be altered and brought closer to the fixed point. The latter strategy was employed to control interbeat intervals of the pulsating activity in living tissue for cardiac arrhythmia stabilization purposes in accordance with real-time calculation with sufficient rapidity to implement corrective control, as disclosed in the aforementioned Spano et al. patent.
A significant characteristic of a neural system associated with brain tissue is the presence of brief aperiodic bursts of focal neuronal activity, referred to as interictal spikes. Such interictal spikes occur between epileptic seizures arising because of nervous system disorders. It is therefore an important object of the present invention to provide a procedure for manipulating chaotic activity, based on the aforementioned study of chaotic regimes, by intervention at irregular times determined from real time calculations involving data obtained by monitoring of brain tissue behavior.